When a dataset comes back from a query/move/etc, the result can either be *stored entirely in memory, or could be stored on disk. This class provides *a mechanism to indicate what the ULConnectionManager should do with datasets *that are produced through query results. *The ULConnectionManager will call the HandleDataSet function during the course *of receiving datasets. Particular implementations should fill in what that *function does, including updating progress, etc. *NOTE: since cmove requires that multiple event loops be employed, *the callback function MUST set mHandledDataSet to true. *otherwise, the cmove event loop handler will not know data was received, and *proceed to end the loop prematurely.